The present invention relates generally to a novel construction of gear pump, and, more specifically, to a gear pump wherein two intermeshing, fluid-conveying gears arranged within the pump chamber or space of a housing, are each arranged upon a respective shaft which has operatively associated therewith at the one side of the related gear a shaft bearing and between such shaft bearing and the gear there is provided a slide or sliding ring packing or seal.
In contrast to gear pumps whose shaft bearings are arranged in the pump chamber, for instance as taught in German patent publication No. 2,649,130, gear pumps of the here described type are also suitable for fluid media which, by virtue of their viscosity and/or their corrosive behavior, must be maintained out of contact with the shaft bearings. With a heretofore known gear pump of the type under discussion as disclosed in U.S. Pat. No. 2,369,249 both of the shafts, to each side of the pump chamber, are extended through a respective packing or stuffing box and in spaced relationship from both sides of the housing are mounted in shaft bearings completely separated from the housing. With this arrangement even small quantities of the conveyed medium, which can escape through the packing boxes, cannot reach the shaft bearings. However, with this design there must be tolerated a large spacing of the shaft bearings, and therefore, such type gear pump only can operate at a moderate pump pressure, since the radial forces acting upon the fluid conveying gears, in the presence of high pump pressures, would bend the shafts in a manner which would impair the effectiveness and service life of the packing or stuffing boxes. With pronounced bending of the shaft there would even be present the danger of freezing of the bearings.
The same is equally true for a different state-of-the-art gear pump construction of the previously described species, as disclosed in U.S. Pat. No. 3,526,470. Here, each of both shafts carries an auxiliary gear in spaced relationship and adjacent the fluid conveying gear attached to the related shaft and is mounted at both sides of such auxiliary gear in a housing part which is separated from the pump chamber by sliding ring seals which are effective in radial direction. With this arrangement both of these shafts are sufficiently rigidly designed and mounted at the region of the auxiliary gears which synchronize such shafts. Yet, the large bearing spacing of the fluid conveying gears only permits operation at moderate pump pressures, since at higher pump pressures the forces acting upon the fluid conveying gears bend the shafts in a manner that there is impaired the service life of the sliding ring seals which are effective in radial direction. Furthermore, the sliding ring seal arranged at each shaft, forwardly of which there is mounted a stripper, can only incompletely protect the shaft bearing, so that during the pumping of highly corrosive liquids it is to be expected that bearing damage will soon arise.